String manipulation in js (interception)

JavaScript substring() method

 

 

stringObject.substring(start,stop)

 

 

Definition and Usage

The substring() method is used to extract characters in a string between two specified subscripts.

illustrate

The substring returned by the substring() method includes the characters at start but not the characters at stop .

If the parameters start and stop are equal, then the method returns an empty string (that is, a string of length 0). If start is greater than stop , the method swaps the two parameters before extracting the substring.

Tips and Notes

Important: Unlike the slice() and substr() methods, substring() does not accept negative arguments.

 

JavaScript substr() method

stringObject.substr(start,length)

 

start	Required. The starting subscript of the substring to extract. Must be a numeric value. If negative, the parameter specifies the position from the end of the string. That is, -1 refers to the last character in the string, -2 refers to the second-to-last character, and so on.
length	Optional. The number of characters in the substring. Must be a numeric value. If this parameter is omitted, the string from the beginning to the end of stringObject is returned .

 

return value

A new string containing length characters starting at start of stringObject (including the character pointed to by start) . If length is not specified , then the returned string contains the characters from start to the end of stringObject .

 

Tips and Notes

 

Note: The arguments to substr() specify the start position and length of the substring, so it can be used in place of substring() and slice().

Important: ECMAscript does not standardize this method and therefore deprecates its use.

Important: In IE 4, the value of the parameter start is invalid. In this BUG, ​​start specifies the position of the 0th character. In later versions, this bug has been fixed.

Example 1

In this example, we will use substr() to extract some characters from the string:

<script type="text/javascript">

var str="Hello world!"
document.write(str.substr(3))

</script>

 output:

lo world!

Example 2

In this example, we will use substr() to extract some characters from the string:

<script type="text/javascript">

var str="Hello world!"
document.write(str.substr(3,7))

</script>

  output:

lo worl (space counts as one character)

Example 3

In this example, we will use substr() to extract some characters from the string:

<script type="text/javascript">

var str="Hello world!"

document.write(str.substr(-5,1))

</script>

 

  output:

o (negative numbers are truncated from the back)

Example 4

In this example, we will use substr() to extract some characters from the string:

<script type="text/javascript">

var str="Hello world!"

document.write(str.substr(-5))

</script>

 

  output:

orld!